According to conventional practices, semiconductor devices are formed on substrates, which are sometimes referred to as wafers. The substrates are thin and disk-shaped and are usually formed of silicon.
Semiconductor manufacturing requires that a number of processes, such as deposition, etching, photolithography, chemical-mechanical polishing and edge cleaning be performed with respect to a substrate. Typically the various processes are performed in various locations or chambers and accordingly the substrate must be transported from one location to another. It is conventional to employ automatic transport devices, such as robotic devices, to transport the substrate from one processing location to another.
Although automatic transport of substrates is designed to be precise and repeatable, it is known that inaccuracies in automatic placement and positioning of substrates do occur. When a substrate is placed inaccurately, processing of the substrate, such as edge cleaning, may be adversely affected. A substrate that has been inaccurately placed may be mishandled and even dropped and damaged, by a device to which the substrate is handed off. Accordingly, it is known to include in substrate-handling devices a mechanism to precisely position or center a substrate relative to a device that is handing off or receiving a substrate. Examples of prior art substrate centering mechanisms are disclosed in published Japanese Patent Application Nos. SHO 60-257134 and HEI 4-30553.
In another conventional arrangement, a centering ring is provided. The substrate is placed on the centering ring and slides down to a centered position defined by the centering ring. However, the sliding of the substrate on the centering ring may generate particles which may contaminate the substrate.
Prior art substrate centering mechanisms may be undesirably complicated and/or may fail to reliably and repeatably center substrates and/or may increase the possibility of substrate contamination. Accordingly, it would be desirable to provide an improved substrate centering mechanism.